Here we have a little mod for XPERIA X1 internal speaker, if the built-in one is not loud enough for you – change it with another 😛 some polish modders from sexperia.eu just tested it and the result is – a way better sound. All you need to do is to open the phone, get a soldering iron and new speaker (here we have one from Motorola K1 and Motorola E398).
You can see the difference, a bigger speaker = better sound 🙂
Another step to do – free some space for the new speaker, you need to remove some of the plastic.
This is the soldering (with E398 speaker inside).